Optimization for designing the waveguide of 980 nm AlGaAs/InGaAs semiconductor laser

Abstract

In order to raise the laser power and improve the far-field characteristics, a new method for designing the waveguide of 980nm AlGaAs/InGaAs semiconductor laser is demonstrated. Theory analysis shows the smaller the confinement factor is, the greater laser power will be. The confinement factors and near field profiles for various optical modes are simulated. The main factors influenced outpower are the fundamental and second order modes. To suppress the mode competition, the position of quantum well was optimized, common symmetric waveguide is replaced by the asymmetric one based on the distribution of various modes in optical field. The simulated results show threshold current (Ith) of the optimized structure is decreased from 230mA to 191mA, while the corresponding differential efficiency (ηd) is increased from 0.92W/A to 1.05W/A. Additional, the vertical divergence angle is reduced from 33.4° to 25.0°, compared to the common one. The designed device structure is grown by solid source molecular beam epitaxy (MBE) system. The fabricated asymmetric waveguide 980nm laser diode with 100μm strip width and 1000μm cavity length has threshold current 210mA, slope efficiency of 0.85W/A. The method for designing the waveguide structure can efficiently increase the loss of high order modes, lower the threshold current, improve the output power and far-field characteristics, which is applied to any kind of edge emitting lasers or laser bars.